This invention generally relates to a liner assembly for a duct, and more particularly to a liner assembly including an acoustically active retainer.
Conventional turbine and turbofan engines for aircraft include a plurality of fan blades that rotate within a duct commonly known as a fan case. The fan case serves as a protective covering to protect the fan blades and the aircraft. Further the fan case channels airflow into the turbine engine. The inner surface of the fan case is constructed to withstand impacts from objects that may come into contact with the fan case and includes acoustical features to reduce noise emitted from the engine.
The acoustical features include a layer of noise attenuation structures covered by a protective face layer including a plurality of openings. The face layer is typically a thin sheet of metal or composite material mounted over the noise attenuation structure. Noise causing pressure disturbances emanate through the openings within the face layer into the noise attenuation structure where the pressure disturbances dissipate to reduce the total amount of noise.
The fan case liner includes seams between the several pieces of material used to form the protective face layer. These seams typically are required to accommodate assembly of the noise attenuation structure and face layer. The seam is covered with a mechanical retainer that is bonded to the face layer on either side of the seam. The mechanical retainer covers any underlying openings within the face layer creating an acoustically dead area relative to the rest of the liner assembly. The acoustically dead area reduces the effectiveness of the noise attenuation layer, increasing the total amount of emitted noise.
Accordingly, it is desirable to develop a mechanical joint for covering seams in a liner assembly that is acoustically active to improve noise attenuation properties.